Oil is extracted by drilling a well on an oil field. A sufficient oil pressure will force the oil to flow out naturally for its subsequent processing and/or distillation. However, if there is not sufficient pressure for the oil to flow to the surface and to maintain the production, a sucker rod pump (also known as pump jack, beam pump, horsehead pump, etc.) system is used. This pump is the superficial part of a piston impellent pump.
The sucker rod pump systems are common in oilfield extraction and their size is determined by deepness, inner diameter of tubing inside the well and density or viscosity of the oil to be extracted, where a deeper extraction requires more energy to move greater lengths of fluid column. A rod-crank mechanism converts the engine's rotary movement into an alternate vertical movement that moves the rod of the pump producing a reiterative up-down movement.
Rod pumps are actuated by an engine. Said engine moves a pulley system which in turn is connected to a connecting rod to compensate the weight of the rod string reaching the bottom of the well. The connecting rod moves up and down a crank connected to a beam's end; the other end of the beam has a head. A steel cable connects the head with the polished rod that goes through a sealing box, permitting the movement inside and outside the tubing but not allowing the fluid to escape from the well (the tubing runs until the bottom of the well). On the bottom of the well there is a reciprocating pump, which has two valves: a static valve and a valve on the piston connected to the end of the rods with a superior-inferior path, known as the “traveling valve.”
Once the sucker rod pump systems are installed, the production continues until problems appear, typically on the bottom of the well, with the deposit of substances like carbonates, paraffin, asphaltenes, sand, formation and corrosion residues, and the like.
Due to the deposit of the above-mentioned substances, the standing and traveling valve seats begin to wear out; as well as the spaces between the traveling container and the polished wall of exterior tubing of the reciprocating pump, causing lack of seal and failure to efficiently lift the oil to the surface; or even they get stuck preventing their proper operation. Likewise, the existing gas within the reservoir may lead to cavitations that hinder the pump, where due to the high gas compressibility, the build-up pressure is not sufficient to open the valves and little or nothing is pumped.
When this happens it is necessary to remove all the equipment from subsurface to the surface in order to repair or replace it. This operation is performed with rod equipment consisting of a rig with a winch with sufficient capacity to load all rods in the well. Extraction, substitution and introduction operation is performed in a 2 to 24 hour period, depending on the well's deepness. Then, it is convenient to clean the bottom of the well between each extraction-introduction in order to prevent any damage occur more frequently. Oil well cleaning needs from one to seven days according to the equipment used for cleaning (reparation equipment, line equipment or flexible tubing equipment); this implies costly operations and production loss for a long time.
Prior art typically discloses information about cleaning oil wells, as the U.S. Pat. No. 5,095,976, that brings protection to a cleaning equipment by means of an inner tubing and reciprocating elements.
Document U.S. Pat. No. 7,475,731 discloses an apparatus and method to clean an oil well by means of fluid injection and subsequent sediment suction.
The use of an apparatus to clean oil wells comprising a tubular conveyor extending from surface to the well portion to be cleaned by means of pumps on the bottom of the hole is known from document EP 1852571.
In addition to oil-well cleaning systems and/or methods included in prior art, there are documents protecting systems for a more efficient production of wells by sucker rod pumping, however those systems are susceptible to substance build-up causing lack of seal and consequently it is necessary to disassemble the entire equipment for replacement or maintenance.
A proper pumping system of dual displacement for fluid production of an oil well is described in document U.S. Pat. No. 6,585,049. This document discloses a pump and a dual displacement pumping system, wherein the system includes a subsurface pump, a production tubing column, a surface pumping unit connected to the subsurface pump by means transmitting reciprocating movements. Said document includes the presence of a production tubing column and has a production inside itself and in its annular portion, i.e. the intubation column. As in hydrocarbon extraction systems that include inner tubing in the intubation column, the system of U.S. Pat. No. '049 necessarily requires disassembling and separating the elements of surface and subsurface structure for preventive, predictive or corrective maintenance, that become into production losses.
The system described by U.S. Pat. No. 6,502,639 provides an improved pumping system including a subsurface pump, a tubing column and a surface pumping unit.
Subsurface pump is attached in the well and driven by the tube up and down repetitive movements. Subsurface pump pumps liquids to the surface through the intubation column. This patent describes a system using a tube to “move” a reciprocating pump; however, the system is exclusive for oil extraction and in case of failure or breakdown hindering functions, all the equipment must be disassembled, including that in the subsurface, to be repaired. In addition, the system extracts oil exclusively through concentric tubing leaving free the intubation column.
Thus, the state of the art does not mention a mechanical pumping system with flexible tubing for simultaneous extraction and cleaning of a well, making more efficient the productive process preventing expenses for repair or maintenance.